Mammoth Uncensored Word List:
19 words ending with gy, 16 letters long

aeromicrobiology biogeomorphology chronophysiology dendrochronology dermatopathology ethnomethodology gastroenterology glottochronology hydrometeorology immunohematology macrometeorology microclimatology micrometeorology paleoclimatology psychoimmunology psychophysiology rhinolaryngology sclerochronology zoogeomorphology